This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:
3GPPthird generation partnership projectC-RNTIcell radio network temporary identifierCCEcontrol channel elementCQIchannel quality indicatorD2Ddevice to device (sometimes termed machine to machineM2M or peer-to-peer P2P)DCIdownlink control informationDLdownlink (eNB towards UE)eNBE-UTRAN Node B (evolved Node B)E-UTRANevolved UTRANLTE/LTE-Along term evolution/long term evolution-advancedMMEmobility management entityPDCCHphysical downlink control channelPDSCHphysical downlink shared channelPRBphysical resource blockPUSCHphysical uplink shared channelRRCradio resource controlSC-FDMAsingle carrier frequency-division multiple accessSRscheduling requestTTItransmission time intervalUEuser equipmentULuplink (UE towards eNB)UTRANuniversal terrestrial radio access network
Research is ongoing for integrating new wireless network topologies under the umbrella of existing and evolving cellular wireless systems, as opposed to side by side such as WLAN co-existing with cellular. Such integrated networks are generally termed a heterogeneous network, and by example current development of 3GPP LTE/LTE-A systems are to deploy macro, micro, pico, and femto cells (as well as relay nodes) in the same spectrum being used by the LTE/LTE-A cellular signaling system, but under supervision of the LTE/LTE-A network. In one aspect such deployed cells include local networks of user devices communicating directly with one another in a D2D network, without routing through the cellular infrastructure.
In various implementations the cellular network's supervision can take on different levels and may allow autonomous or semi-autonomous D2D communication. The local D2D terminals may perform certain tasks in a co-operative way, such as spectrum sensing to find temporarily unused portions of the licensed cellular spectrum for their own D2D communications or co-operative downloading or multicasting. One D2D terminal may serve as a gateway for other low-capability devices to access the cellular network.
For simplicity of description only assume there are only two communicating devices forming a D2D network. This D2D network may be given its own temporary identifier (C-RNTI) so that each of the D2D pair can know from a single control message sent by the cellular network (eNB) what radio links/bearers are allocated for their D2D communications. It is reasonable to assume that in some instances the D2D bearer may be allocated by the eNB semi-persistently, to limit control signaling overhead. Conventionally, a user device UE in a cellular network is assigned an individual C-RNTI by which it identifies its individual (cellular) resource allocations. Combining this with the C-RNTI for the D2D network means that a UE operating in both cellular and D2D networks has two C-RNTIs for which to monitor what radio resources the network has allocated to it. In LTE the resource allocations are sent on the PDCCH, and so the above scenario leads to the following issues.
First, there are different PDCCH message required for cellular and D2D radio bearers per TTI if the eNB is to allocate cellular resources and D2D resources to the same UE. This complicates the mapping of PDCCHs to CCE locations respecting the device specific search spaces. Second, the UE will need to search at least for its individual cellular C-RNTI and its D2D-pair C-RNTI. But if the other UE of the D2D pair also has an active cellular link then still the first UE's extended searching might not identify all collisions which might impact the allocated D2D bearers, since the other D2D device might have received an allocation under its individual C-RNTI which the first UE never reads. The eNB can itself assure by its own scheduling that it allocates no overlapping resources, but that constrains the eNB's scheduling flexibility. Maximizing the eNB's scheduling flexibility in the above scenario would result in the power-limited UEs routinely searching multiple search spaces for the various c-RNTIs and still not positively identifying all potential D2D bearer collisions.
Assuming a straightforward extension of LTE practices for the above scenario, the eNB would allocate cellular resources for UL transmissions using DCI Format 0 on the PDCCH using the individual cellular C-RNTIs, and allocate resources for D2D transmissions using DCI Format 0 (or some new DCI format) on the PDCCH using the C-RNTI assigned to the D2D pair. As detailed below the inventors have derived a signaling regimen to support resource allocations for both cellular and D2D links for the UEs in active D2D communication that is more efficient than the above extension of LTE practices, and which embodiments enable the D2D devices to positively identify bearer collisions in all cases.